The present invention relates to an electrical push button switch and more particularly it relates to a push button switch for electronic timepieces having a conductive elastomeric spring.
In the development of electronic watches, utilizing semiconductor integrated circuitry and digital readout devices, such as liquid crystal or light emitting diode displays, the need arose for suitable switching devices by which such watches could be adjusted to display the correct hours, minutes, seconds, date, etc. For some electronic watches, particularly those employing light emitting diode display units, a further switching mechanism was required to activate the display unit momentarily each time that a display of the current time is desired.
Typically, electronic watch circuits are contained in a watch case having an air tight cover, and it is not uncommon that such watches be waterproof and even hermetically sealed. In such watches one prior art approach to the switching requirements, as disclosed in the U.S. Pat. to Bergey, No. 3,782,102, was to employ tiny permanent magnets in a push button device contained on the outside of the watch case. These magnets were positioned so that when the push button was depressed the magnetic field of the permanent magnet in the push button passed through the non-magnetic watch case and attracted a magnetic armature within the sealed watch movement, thereby accomplishing switching. The disadvantages of such a complicated switching device became readily apparent. For one thing, a relatively large number of parts were required for proper functioning of the switch. Also, the watch could not be exposed to magnetic fields since the magnetism of the permanent magnet could likely be altered. Also, two springs were required in order for such a magnetic switch to function: an external spring for biasing the push button outwardly from the watch case and an inward spring for biasing the armature in a position normally away from the position it would be in as a result of the magnetic pull of the push button magnet. Finally, such magnetic switch devices were not only expensive and complicated, but they required precise alignment of the magnet and the armature. The limitations and disadvantages of such switch devices are overcome by the present invention.
Other watch case mounted control switches of the prior art utilized metal parts with very close tolerances, and were press fitted into the watch case. These switches normally utilized a minimum of four separate parts, all of which moved upon one another during any switching operation. The relatively large number of parts as well as the requirement for close tolerances in such switches resulted in relatively high costs. This drawback is likewise overcome by the present invention.
It is therefore one object of the present invention to provide a push button switch for electronic watches that is simple to fabricate and use, and which manifests a long life by having fewer moving parts and thus may be manufactured at substantially lower costs than prior art switches.
Another object of the present invention is to provide a push button switch for electronic watches which is waterproof and which affords a switching function without sacrifice of an air tight seal of the interior chamber of an electronic watch.
Yet another object of the present invention is to provide a push button switch for electronic watches having a moving contact biased by a conductive elastomeric material and adapted to contact an internal metallized switch pad on a printed circuit substrate comprising the electronic circuitry of the watch without need of other fixed or moving parts.